Hello everybody. I'm back into the Mercedes fold, for now. I just piked up a '98 E300 with the OM606 turbo. I'm doing maintenance on it tomorrow and want to investigate a few things while I'm there. I'm doing all of the fuel lines, oil & coolant chain (trans fluid has already been done, I replaced the speed sensor plate not long ago - bought this from a colleague, so it's not a complete stranger to me), fuel filters, rear window regulators...

Does anybody have a diagram or p/n's for all of the PCV stuff on top of the engine? It's all oily, so I assume it leaks. if it's all cheap enough I'll just buy it all new.

I want to delete the EGR. Does the ECU use the MAF for anything besides EGR? Is there a tuner that can turn of the codes for EGR?

Diesel purge. 1 can or 2? Hooked up the way I've seen in some videos putting 2 hoses into the bottle, is that cleaning the injection pump too, or just the injectors? Is there anything I should be concerned with in the tank?

Tuning/software. Who are the recommended tuners around here? Not going for big HP, but a few more ponies and a few mpg gains would be nice (and getting rid of the pesky emissions equipment, of course).

EGR Delete here

I have done it, no codes, works perfectly

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1999 Mercedes E300TD daily driver sold at 238K miles 106K miles were mine, rust worm got it :-(
2006 Mercedes CDI new daily driver! 56,000 miles May 2016 now 85,625 Apr 2018 and Apr 2019 101,000 miles Apr 2020 109,875. March 2024 135,250, Dec 2024 145,000 miles

Thats a long read, thanks. I'll look into it, but if it can be done in the ECU with a flash I'd rather just do that.

Look at the diagram on the page EDBSO linked to. No need to read the whole thread. It's literally one diode and one resistor. Doesn't get much easier than that. Installed it a few months ago myself, and disconnected vacuum from the EGR valve so it will never open. No codes set.

While you're in there replacing the plastic fuel lines, swap the o-rings out for viton. I bought mine from fryer power, a nice complete kit: Viton for Mercedes Engines at FRYERPOWER HOME

For ECU tuning, you need someone who will replace the soldered on chips, with a pair of sockets. I know Jeff at Rocketchip has the equipment and expertise to perform this correctly. I've used him a number of times for VW TDI's, very satisfied, I'll be going back to him with my E300. He can dial the EGR duty cycle down to zero too, if you prefer this approach over the diode-and-resistor solution.

As for the PCV, it's only a few parts on our turbos. 65, 68, 71, 74 in the diagram. Thankfully unlike the internet of pipes and junctions like the normally aspirated 606 had.

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1998 E300 turbodiesel

America's Rights and Freedoms Are Not The Enemy!

I understand what the resistor/diode mod is, but as stated - if there's an ECU flash option, I'd prefer to do that instead.

Thanks for the link. I'll investigate these orings.


Oh, thats for the pic in the edit. Where do I find p/n's for those? I can't find them in my Worldpac Speeddial anywhere.

The fuel line that goes from the motor side of the shut off valve to the fuel filter is secured by a banjo bolt. There is a small lime colored o ring at the end of the banjo bolt. Buy one of those when you get your fuel line. Mine broke when I removed the banjo bolt, and I had to make a special trip to the dealer to buy a new one. When you change the fuel lines, put a new o ring on the connection between the shut off valve and the injection pump. That o ring causes lots of problems.

Check your shut off valve for cracks. You can do that by wiping it off and inspecting it and then trying, as best you can, to fill it with diesel fuel.

While you've got the intake manifold off, you should consider changing the glow plugs. The added cost is about $90 for the glow plugs and $50 for the reamer. There is a Pelican wiki paper on changing glow plugs and several instructive threads in this forum. Read the threads, because you can run into big trouble if you break a glow plug trying to remove it.

Also, the temperature gauge sender unit is under the intake manifold. If your temperature gauge is acting up, you may want to change it.

Do I need to pull the intake to get to all of the plastic fuel lines? If so, then ya I'll definitely just do the glowplugs while I'm there. I'm very familiar with how to do them. Had one break off in a friends and it took a long drill bit and a slide hammer moving the entire car to get it out.

Thinking of the intake manifold....the entire drivers side of the engine and intake piping is covered with oil & nastyness. I presume this is coming from the EGR or some other way out of the intake? I assume this is common, so maybe somebody can point me in the right direction there?

Yes intake must come off to replace the plastic fuel lines. And FWIW the fryerpower viton kit includes the two o-rings ESchwab mentioned. You will need to source your own copper crush washers though, two of them, for the banjo fitting.

I would also heed his advice re: the cylinder head temp sensor. It's inexpensive, but you have to remove the intake to access it, so might as well replace it preemptively while youre in there.

Yes this is common, there's a large o-ring that sits between the EGR valve and the piping. When the o-ring fails, it makes a mess as you describe. Replace the o-ring while you have the intake off. p/n 606-997-06-45

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1998 E300 turbodiesel

America's Rights and Freedoms Are Not The Enemy!

For me that would be a whole lot of stuff to do in one sitting. What I mean is if you have any problem after work is done, was is something I did and where to start looking. I know it's nice to do a bunch of stuff at once but could be harder to diagnose any problems after the work.

I'm a mechanic by trade and own a small shop, but overly anal about my own cars. Tearing the engine down and reassembling is not a problem. I'm just looking to arm myself with as much info as possible before I get started

you did things the hard way for no reason. everyone around here will tell you penetrating oil and a ratchet and hope for the best. the way that has a 100% guarantee is using an impact gun between 30-40 psi with a fully heated up engine and they will come out (all 6) within 45 minutes. i've done it 3 times and walked a member through the process who vouches for my technique.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

The glow plug was already broken when I was asked to assist. Don't make assumptions

A trick I use and highly recommend is to fill the fuel tank to the top, my drive slopes down so I start with the car level in the garage and after replacing the fuel filter and/or fuel lines I roll it down the driveway and start with the nose down and tank high. Yes have a fully charged battery.

The intake manifold comes off and goes on real easy and the gasket is cheap, you will not believe the gunk built up in there.

Heard more bad than good things about having the car remapped, usually causes some driving anomalies or quirks if you prefer.

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1999 Mercedes E300TD daily driver sold at 238K miles 106K miles were mine, rust worm got it :-(
2006 Mercedes CDI new daily driver! 56,000 miles May 2016 now 85,625 Apr 2018 and Apr 2019 101,000 miles Apr 2020 109,875. March 2024 135,250, Dec 2024 145,000 miles

Such as? Links? A tune is usually one of the first things I do to a new (to me) car. While factory tunes on newer vehicles have gotten quite good on modern cars with full widebands stock etc., the OE still has to make compromises that aren't always ideal for best running conditions. Doesn't help, I suppose, that my best friend is one of the best BMW tuners in the country, and a majority of the past god knows how many cars I've had have been BMW's.... That, and I'm just not a fan of 'fixes' that fool the ECU. Garbage in, garbage out is never a good way to go, so if there's a way to fix the issue in the software itself, thats always better.

Happy with my Rocketchip tune on my 98. Stage 2 gave me marked (though not dramatic) improvement. I was hoping for fuel economy improvement but didn't see any.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 178k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 75k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife